JPS6096751A - Heat resistant structure - Google Patents

Abstract

PURPOSE:To provide a heat resistant structure excellent in high temp. durability, obtained by forming a cerium oxide coating layer to the surface of a structure comprising a heat resistant alloy through a bonding layer. CONSTITUTION:An adequately selected heat resistant alloy (IN939 etc.) is formed into a structure having a predetermined shape and, if necessary, sand blast treatment is applied to the surface thereof and a bonding layer is formed thereto by a plasma spray method. The bonding layer is formed of an Ni-base alloy or a Co-base alloy and uniformly formed in a thickness of about 30-300mum. Subsequently, cerium oxide is uniformly applied in a thickness of about 50- 500mum to form a coating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a heat-resistant structure, and more particularly to a heat-resistant structure in which the high-temperature durability of a heat-resistant alloy component is improved by improving a ceramic heat-resistant coating layer.

[Technical background of the invention and its problems]

Heat-resistant structures are commonly used for heat-resistant alloy parts such as gas turbine parts. For example, in the case of gas turbine parts, gas temperatures reach over 1400°C, so heat-resistant structures with excellent high-temperature properties that can withstand the harsh operating conditions are used. A structure is required.

In the past, various studies have been conducted on heat-resistant structures with excellent high-temperature properties, including methods using ceramic materials such as silicon nitride (SL 8N4) and silicon carbide (5iC) as structural materials, and methods for cooling heat-resistant alloys. However, proposals have been made for methods of using it as a high-temperature member, and methods of coating it with heat-resistant ceramics that take advantage of the low thermal conductivity of ceramic materials. However, proposal (1) is still in the research process and has not yet been put into practical use, and proposal (2) suffers from a problem of reduced thermal efficiency due to cooling, so in the end, proposal (3) However, heat-resistant coating, which is currently attracting the most attention, is a method in which ceramics with low thermal conductivity are coated on conventional heat-resistant alloys to protect the base alloy from high heat. Ceramic generally has a low coefficient of thermal expansion, and the ceramic layer tends to peel off due to the difference in thermal expansion with the ceramic-coated temporary base alloy. Therefore, it is desirable that the ceramic material applied to the heat-resistant coating not only have low thermal conductivity but also have a coefficient of thermal expansion close to that of the heat-resistant alloy.

Therefore, ZrOx has conventionally been used as a ceramic material for heat-resistant coating.

However, since ZrO undergoes a phase transition at about 100°C and about 1200°C, Y2O,...
While it is essential to dissolve MgQ, CaO, etc. in solid solution, these solid solution components are lost during long-term practical use at high temperatures, and from the viewpoint of durability, this has been a factor that limits the service life.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned drawbacks and to provide a heat-resistant structure having excellent high-temperature durability by improving the ceramic heat-resistant coating layer.

[Summary of the Invention] The heat-resistant structure of the present invention is characterized by comprising a structure made of a heat-resistant alloy and a cerium oxide coating layer provided on the surface of the structure via a bonding layer.

The structure made of a heat-resistant alloy of the present invention is a heat-resistant alloy formed into a general predetermined shape depending on the use. There are no particular limitations as long as it is something. Specific examples of this heat-resistant alloy include IN939 and IN737B.
:Ni-based heat-resistant alloy such as LC-' or X-40', M
Examples include Co-based heat-resistant alloys such as AR-M-509.

The bonding layer of the present invention serves to alleviate thermal stress caused by the difference in thermal expansion between the structure made of a heat-resistant alloy and the cerium oxide coating layer. Therefore, it is desirable that the material used for the bonding layer has an expansion coefficient intermediate between that of the heat-resistant alloy base material and that of the base material of the heat-resistant coating layer. Specific examples of this material include Nl-based or Co-based alloys, ? 'JiCrA/,Y
Or CoCrAtY alloy, etc. can be mentioned.

The coating layer of the present invention is formed using cerium oxide as its material. For reference, the physical properties of cerium oxide show that the thermal conductivity of the sintered body is approximately IW/-
It is extremely preferable as a material for the heat-resistant coating layer because it has a small m2 of less than 1/1o of stainless steel and a coefficient of thermal expansion of approximately 14×10, which is similar to that of a heat-resistant alloy.

Next, a method for manufacturing a heat-resistant structure of the present invention will be explained. First, an appropriately selected heat-resistant alloy is formed into a structure of a predetermined shape by a conventional method, and the surface is coated with alumina (A40
m) A bonding layer may be provided after sandblasting with particles or the like to make the surface suitable for thermal spray coating.

This bonding layer may be formed by any commonly used method, such as thermal spraying, diffusion coating, CVD, vapor deposition, PvD, and the like. Among these methods, the thermal spraying method is preferred because it is suitable for increasing the film thickness formation rate. Moreover, the thickness 2 of this bonding layer is 30 to 300μ
m, preferably 50 to 200 μm. If the thickness is out of the above range, the effect of the bonding layer will be small or the adhesive strength of the bonding layer will tend to decrease, which is a problem for the cinema. Furthermore, it is desirable that the shape of this bonding layer is uniform on the surface of the structure. After applying this bonding layer, cerium oxide is subsequently applied as a heat-resistant coating layer to obtain the heat-resistant structure of the present invention.

The coating layer may be formed by applying the method for forming the bonding layer described above and finishing it. Moreover, the thickness of this coating layer is 50 to 500 μm.

Preferably it is 200 to 300 μm. When the thickness is outside the above range, the heat resistance effect tends to be weakened or the adhesive strength of the coating layer tends to decrease, which is not preferable. Furthermore, it is desirable that the shape of this coating layer is uniformly applied to the surface of the bonding layer.The present invention will be described in more detail below with reference to examples of the present invention.

[Embodiments of the invention]

Example 1 As a structure made of a heat-resistant alloy, an N1-based alloy having the composition shown in Table 1 was cut into 50 x 10 x 3 (tJ), and its surface was coated with A403 particles with a grain size of about 1 m using sandoplast. Processed. Then, on the surface of the Ni-based alloy, a bonding layer of Ni-17Cr-AL-0,
6Y alloy powder was sprayed using a plasma spraying device at a spraying distance of 125 mm.
m, about 100μ under the conditions of current value 700A and voltage value 34V.
Thermal spray coating was applied to a thickness of m. Furthermore, CeO2 powder was sprayed onto the bonding layer using the same apparatus at a spraying distance of 80cm, a current value of 800A, and a voltage value of 37V to form a % CeO□ layer to a thickness of about 300μm. A heat-resistant structure was obtained. Regarding the obtained heat-resistant structure, the following evaluation test was conducted to confirm high-temperature durability.

Thermal conductivity test: The thermal conductivity of the heat-resistant coating layer made of cerium oxide was measured by a laser flash method. At the same time, as a comparative example, the thermal conductivity of a heat-resistant coating layer made of ZrO-8Y2O2 and a Ni-based alloy was measured in the same manner.

Thermal shock test - The test piece was tested at 1080℃ for 60 minutes in the atmosphere.
Repeat the thermal shock test by heating for 60 minutes and cooling at 280°C for 60 minutes, and count the number of times a<p until cracking is observed with the naked eye.

The results are shown in Table 2.

Table 1 Table 2 Example 2 Ni sandblasted under the same conditions as Example 1
Ni-17Cr-6 was applied to the surface of the base alloy under argon atmosphere of 200 Torr under 37V800A+7) conditions.
At-0,6Y alloy powder was thermally sprayed to a thickness of about 100 μm. Furthermore, under the same conditions as in Example 1, CeO
, a heat-resistant coating layer was formed to obtain a heat-resistant structure of the present invention.

Regarding the obtained heat-resistant structure, the following evaluation test was conducted in order to confirm high-temperature durability.

Oxidation test: The heat-resistant structures obtained in Examples 1 and 2 were held in a furnace at 1080° C. in the atmosphere, and the time until cracks were observed (to the naked eye) was measured.

The results are shown in Table 3.

〔Effect of the invention〕

As detailed above, the heat-resistant structure of the present invention has much better high-temperature durability than conventional ceramic heat-resistant structures, and its industrial value is extremely large.

Claims (1)

[Claims] 1. A heat-resistant structure comprising a structure made of a heat-resistant alloy and a cerium oxide coating layer provided on the surface of the structure via a bonding layer. 2. The heat-resistant structure according to claim 1, wherein the coating layer is formed by a thermal spraying method. 3. The heat-resistant structure according to claim 1 or 2, wherein the bonding layer is formed by thermal spraying in an inert atmosphere of 10 to 350 Torr.